In fluid systems the pressure relief valve is designed to limit the system pressure to a certain predetermined pressure level. When this predetermined value is reached, the pressure relief valve responds and routes the excess volumetric flow, that is to say, the difference flow between the pump flow and consumer flow, from the fluid system toward the tank side. In addition to the pilot-controlled pressure relief valves which will not be explained in greater detail. Directly controlled pressure relief valves, viewed dynamically, act as a spring-mass system executing vibrations when set into motion. These vibrations also act on the prevailing fluid pressure and must be balanced appropriately by damping. In this connection, the impulse forces of the fluid flow are used to virtually balance the increase of the spring force in operation of the valve.
To obtain good pressure setting and a flat Δp-Q characteristic (pressure increases as small as possible with increasing volumetric flow) over the entire pressure range, the entire pressure range can be divided into pressure increments. The maximally adjustable pressure is determined from the maximum magnetic force (force at the rated current of the solenoid system) and the area of the valve seat active for pressure (circular area of the seat diameter) according to the following formula:
      p    max    =                    F                  Magnet          ,          max                            A        seat              =                            F                      Magnet            ,            max                          ·        4                              D          seat          2                ·        B            
In a plurality of embodiments of these valves, providing an electrically triggerable solenoid system with an actuating coil to trigger the valve element is known in the prior art.
In one known solution available on the market, the valve element in the form of a closing part with a tapering closing cone is directly tied to the rod-shaped actuating part of the solenoid system. In operation of the valve, this arrangement can lead to instabilities due to the mass inertia of the armature in the form of an actuating part. The resulting friction between the actuating part and the valve closing element also leads to increased hysteresis in valve operation.
In the prior art it has already been proposed, to stop this unstable behavior, that the solenoid system be decoupled from the actual valve unit by an energy storage device in the form of a compression spring supported on the end sides on the interior of the valve housing and on the valve element itself to avoid instabilities. Based on dimensional tolerances alone, in particular for increasing fluid volumetric flows, angular displacements between the axis of the closing cone and the actual direction of travel of the valve closing element occur. The closing cone then may not be able to exactly block or could even damage the edge of the valve seat assigned to it in the housing, with the result that the valve then can no longer effect a leak-proof seal.